Fix broken link in error codes doc and support doc (#6196)

[ti-chi-bot]

This is an automated cherry-pick of #6196

What is changed, added or deleted? (Required)

Fix a broken link

Alternative targets:

• https://dev.mysql.com/doc/mysql-errors/5.7/en/server-error-reference.html
• https://dev.mysql.com/doc/mysql-errors/8.0/en/

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)
• v4.0 (TiDB 4.0 versions)
• v3.1 (TiDB 3.1 versions)
• v3.0 (TiDB 3.0 versions)
• v2.1 (TiDB 2.1 versions)

What is the related PR or file link(s)?

Closes #6194

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• TomShawn

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[TomShawn]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Details

Commit hash: 5dfa4aa